Chlorine electrolysis cells

Fig. 26.8. Chlorine electrolysis cells (a) membrane cell (b) diaphragm cell (c) mercury cell.

Fig. 5. Chlorine electrolysis cells. Courtesy of McGraw-Hill, Inc.

Aqueous Hydrochloric Acid. Muriatic acid consumption in 1993 was about 1.57 million metric tons (100% basis). The largest captive use of aqueous HCl is for brine acidification prior to electrolysis in chlorine/caustic cells and the largest merchant markets for HCl are steel pickling and oil-well acidizing, which accounted for 25 and 16% of merchant production, respectively, during 1989. 

Platinum Platinum-coated titanium is the most important anode material for impressed-current cathodic protection in seawater. In electrolysis cells, platinum is attacked if the current waveform varies, if oxygen and chlorine are evolved simultaneously, or if some organic substances are present Nevertheless, platinised titanium is employed in tinplate production in Japan s. Although ruthenium dioxide is the most usual coating for dimensionally stable anodes, platinum/iridium, also deposited by thermal decomposition of a metallo-organic paint, is used in sodium chlorate manufacture. Platinum/ruthenium, applied by an immersion process, is recommended for the cathodes of membrane electrolysis cells. ... 

Balko, E.N. (1979) SPE hydrochloric acid electrolysis cells performances. Cell Configuration, Oronzio DeNora Symposium - Chlorine Technology. See United States Patent No. 4,311,568 and United States Patent No. 4,294,671. 

Viton hoses were instead selected for the feed brine to the electrolysis cells. These are chemically resistant to chlorine-containing brine. There are several specifications of Viton hose available. For working with brine in an electrolysis environment, special attention had to be given to rupture resistance of the hoses with respect to operator safety. 

An additional advantage of the hypochlorite recycling process is the chlorination of the feed brine in the brine-degassing unit. Organic and nitrogen-containing components are oxidised. The reaction products are removed via the vent-gas to the chlorine destruction unit. Less NCI3 is formed in the electrolysis cells because part of the... 

An additional advantage is the oxidation of all organic and nitrogen-containing components of the brine in the brine degassing tanks. These impurities are not fed to the electrolysis cells, but the products removed to the chlorine destruction unit and incinerator. Control of NCI3 concentrations in chlorine liquefaction has become easier. 

Development of chlorine electrode materials has benefited from the experience of chlor-alkali electrolysis cell technology. The main problem is to find the best compromise between cycle life and cost. Porous graphite, subjected to certain proprietary treatments, has been considered a preferable alternative to ruthenium-treated titanium substrates. The graphite electrode may undergo slow oxidative degradation, but this does not seem to be a significant process. 

Chlorine gas is evolved at the anode of a commercial electrolysis cell at the rate of 3.65 L/min, at a temperature of 647°C. On its way to the intake pump it is cooled to 63°C. Calculate the rate of intake to the pump assuming the pressure has remained constant. 

Summary Sodium hydroxide can be prepared by electrolyzing a sodium chloride solution in a two-compartment cell separated by a porous membrane. Chlorine gas is liberated at the positive anode and hydrogen and sodium hydroxide are liberated at the cathode. Use proper ventilation when running the electrolysis cell because of chlorine and hydrogen gas evolution. Run the cell in an area that is away from direct sunlight. 

Currently the chlorohydrin process is only used for the epoxidation of propylene, where it still accounts for some 48% of world installed capacity. The yields are 88-89%. In most cases, the plant is integrated with a chloro-alkali facility that supplies both the required chlorine and sodium hydroxide. The recycle to the electrolysis cells of the brine solution produced in the dehydrochlorination step has been considered but not applied, most probably, for technical and economic reasons. In general the aqueous solution of calcium or sodium chloride is disposed of. 

Considering reactions (1) and (2), chlorine and sodium amalgam are formed in the electrolysis cell. The amalgam can be extracted and undergoes a decomposition reaction in a separate reactor (decomposer, denuder). The electrocatalytic process is... 

As the products chlorine on the one hand and hydrogen and alkali on the other originate at different places, electrolysis cell and decomposer, there is no problem of separation. 

The most important commercial application of perfluorinated ionomer membranes is currently in the chlor-alkali industry. These materials are used as permselective separators in brine electrolysis cells for the production of chlorine and sodium hydroxide. This... 

The use of electrochemistry to convert propylene to the oxide was researched in particular by Bayer and Kellogg. In this method, propylene is injected in the neighborhood of the anode of a sodium chloride electrolysis cell with a mercury athode (see Section 11.2.5.ZB). The hypochlorous add formed with the chlorine liberated at the anode is added to the propylene. The chlorohydrin obtained is hydrolysed at the cathode by the caustic produced by the action of water on the amalgam. Propylene oxide is separated from the mixture by stripping, while the. sodium chloride is returned to the electrolyser. The overall reaction is as follows ... 

The electrolytic production of chlorine and caustic soda using a cation-exchange membrane as a separation medium is already a technically and commercially well established process [54, 56]. The principle of the process is illustrated in the schematic drawing of Figure 16, which shows an electrolysis cell arrangement consisting of two chambers separated by an cation-exchange membrane. 

A couple of hydrogen accidents were associated with the chlorine production by chloralkali electrolysis, which are included in Table 8-4 under Electrolysis malfunction . Fire or explosion occurred when for some reason, for example a reversal of cell polarity, the hydrogen entered the chlorine processing equipment downstream of the electrolysis cells [104]. 

Price advantage for magnesium amounting to up to one third over sodium, can be expected when recycling anhydrous magnesium chloride on a sufficiently lar e scale through fusion electrolysis cell, which also yields a usable chlorine... 

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